title: A missense mutation at Ile172----Asn or Arg356----Trp causes steroid 21-hydroxylase deficiency.
abstract: Congenital adrenal hyperplasia (CAH) is a common recessive genetic disease caused mainly by steroid 21-hydroxylase (P450c21) deficiency. Many forms of CAH exist resulting from various mutations of the CYP21B gene. We sequenced CYP21B cDNA from a normal person and its genes from a patient with simple virilizing CAH. When comparing several CYP21B sequences, we found it was polymorphic. In the patient, a single base substitution replaced Ile172 (ATC) with Asn (AAC) in one allele while Arg356 (CGG) was converted to Trp (TGG) in the other. A normal P450c21 cDNA clone was transfected into COS-1 cells to produce 21-hydroxylase activity toward its substrates, progesterone and 17-hydroxyprogesterone. Mutants corresponding to Asn172 or Trp356 mutation were constructed by site-directed mutagenesis of the normal c21 cDNA clone. They failed to produce active enzyme toward either substrate upon transfection into COS-1 cells, demonstrating that these mutations caused CAH. Aligning sequences with other P450s, Ile172 could be located in the membrane anchoring domain and Arg356 in the substrate-binding site of P450c21. Both mutations are present in the CYP21A1P pseudogene, suggesting that they may be transferred from CYP21A1P by gene conversion events.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: S H
authors.initials: SH
authors.lastname: Chiou
authors.forename: M C
authors.initials: MC
authors.lastname: Hu
authors.forename: B C
authors.initials: BC
authors.lastname: Chung
mesh_terms: D000293:Adolescent; D000312:Adrenal Hyperplasia, Congenital; D001120:Arginine; D001216:Asparagine; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D004247:DNA / Q000235:genetics; D005260:Female; D005796:Genes; D006801:Humans; D007532:Isoleucine; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010957:Plasmids; D012016:Reference Values; D015183:Restriction Mapping; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D013250:Steroid Hydroxylases / Q000235:genetics*; D014162:Transfection; D014364:Tryptophan
chemical_list: D003062:Codon; D015345:Oligonucleotide Probes; D007532:Isoleucine; D001216:Asparagine; D014364:Tryptophan; D004247:DNA; D001120:Arginine; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase